Photoflash lamp



Obt- 20, 1970 F, ANDERSON ETAL I 3,535,063

PHOTOFLASH LAMP Filed Aug. 30. 1968 INVENTORS T LESTER E ANDERSON SEDGWICK R. BENNETT JOHN W. SHAFFER mw (i M ATTORNEY United States Patent 3,535,063 PHOTOFLASH LAMP Lester F. Anderson, Sedgwick R. Bennett, and John W.

Shaffer, Williamsport, Pa., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Aug. 30, 1968, Ser. No. 756,516 Int. Cl. F21k 5/02 US. Cl. 431-93 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the manufacture of photoflash lamps and more particularly those of the percussive type.

Generally speaking a percussive-type photoflash lamp comprises an hermeticaly sealed, light-transmitting envelope containing a source of actinic light and having a primer secured thereto. More particularly, the percussive-type photoflash lamp may comprise a length of glass tubing constricted to a tip at one end thereof and having a primer sealed therein at the other end thereof. The length of glass tubing which defines the lamp envelope contains a combustible such as shredded zirconium foil and a combustion-supporting gas such as oxygen. The primer may comprise a metal tube and a charge of fulminating material on a wire anvil supported therein. Operation of the lamp is initiated by an impact onto the tube of the primer to cause deflagration of the fulminating material on the wire anvil up through the tube to ignite the combustible disposed in the lamp envelope.

Heretofore, in lamps of this type the anvil was a straight length of wire dropped into the primer tube and crimped near the bottom of the tube to support it therein. This arrangement never proved entirely satisfactory for several reasons. Frequently the fulminating material ignited during insertion and crimping of the wire anvil. Movement of the wire anvil and subsequent indefinite positioning of the fulminating material resulted in poor lamp reliability. Such lamps were extremely sensitive to jarring and handling, and accidental ignitions were frequent. The fulminating material was applied to the wire in the form of a band by transfer of a droplet while rotating the wire. Poor control of fulminating material weight with this application technique gave rise to highly variable light output and timing from one lamp to another. The tight crimp needed to hold the straight length of wire often resulted in cutting or fracture of the thin tube wall, followed by gas leakage. Molten particles often burned and/ or melted through the tube with a resultant expulsion thereof through the opening produced.

In an effort to improve the weight uniformity of fulminating material from lamp-to-lar'np, the fulminating material was dip-applied to one end of the wire anvil. Thus the quantity of fulminating material applied could now be controlled by varying the rate of withdrawal of the wire anvil from the dip cup. The wire anvil was frictionally held in place by undulations formed therein at the other end thereof and frictionally engaging the inner wall of the tube within which it was disposed, thereby eliminating the problem of tube rupture during crimping. The fulminating material was positioned within the primer tube by causing that end of the wire anvil on which the fulminating material is located to bottom 3,535,063 Patented Oct. 20, 1970 therein. However, this arrangement also was characterized by several deficiencies. The fulminating material frequently ignited during insertion of the wire anvil and the completed lamps were intolerably sensitive to handling. For example, a relatively slight mechanical shock would often flash the lamps regardless of where on the lamp the actual impact occurred.

In view of the foregoing, one of the principal objects of this invention is to provide a percussive-type photoflash lamp that is sufliciently inactive to withstand handling during manufacture and use without premature flashing, but which is highly sensitive toward impact of a firing device.

Another object is to provide a primer construction for percussive-type photoflash lamps that permits automated assembly without igniting the fulminating material thereof.

A further object is to provide a primer construction that affords high lamp reliability.

These and other objects, advantages and features are attained, in accordance with the principles of this invention, by providing the wire anvil with a plurality of spaced protuberances which aid in supporting it inside the primer tube and provide a clearance between the coating of fulminating material and the inner wall of the tube.

In the specific embodiment of the invention illustrated in the accompanying drawing, FIG. 1 is an elevational view partly in section of a percussive-type photoflash lamp with which the wire anvil of this invention may be employed.

FIG. 2 is a fragmentary detail on an enlarged scale of the primer of the lamp of FIG. 1.

The percussive-type photoflash lamp illustrated in the accompanying drawing comprises a length of glass tubing defining an hermetically sealed lamp envelope 2 constricted at one end to define an exhaust tip 4 and shaped to define a press 6 at the other end thereof. A primer 8 is sealed in the press 6. The primer 8 comprises a metal tube 10, a wire anvil 12 and a charge of fulminating material 14. A combustible such as filamentary zirconium 16 and a combustion-supporting gas such as oxygen are disposed within the lamp envelope.

As shown particularly in FIG. 2, the wire anvil 12 is provided with a head 20 at the end thereof which is disposed within the primer tube 10 and protuberances 22 intermediate the ends thereof, with the body of fulminating material 14 located therebetween. The fulminating material 14 may be dip-applied to the wire anvil below the protuberance 22 and subsequently removed from the head 20 so that the entire body of fulminating material is located between the head 20 and the protuberances 22. The diameter of the head 20 and the diameter of a circumscribed circle about the protuberances 22 are larger than the diameter of the coating of fulminating material 14. Contact of the fulminating material with the inner wall of the primer tube 10 is thus avoided by the provided clearance 24. A crimp 26 in the metal tube on or above the head 20, positively anchors the wire anvil 12 and the protuberances 22 stabilize it within the primer tube 10.

A percussive-type photoflash lamp of this construction is far less sensitive to inadvertent ignitions in handling and is therefore more feasible to manufacture and market. At the same time, high sensitivity to deliberate indentation of the primer tube bya firing device is maintained. Clearance 24 greatly reduces accidental ignitions of the fulminating material during insertion of the wire anvil into the primer tube and crimping thereto. The positive and uniform positioning of the fulminating material made possible by this structure provides a much 3 higher lamp reliability. The presence of head 20 also eliminates the need for severe crimping of the primer tube 10 and thus the problem of tube leakage is avoided. Although we prefer the specific structure shown in the accompanying drawing and described in detail above, it will be readily apparent to those skilled in the art that variations are possible without departing from the spirit and scope of the invention. For example, the head 20 could be one or more protuberances of another shape or form and the number and location of the protuberances 22 may vary so long as they maintain the wire anvil 12 in spaced coaxial relation with the primer tube 10 and provide enough unobstructed cross sectional area therein to avoid excessive throttling during defiagration of the fulminating material up through the tube 10.

What we claim is: 1. A photoflash lamp comprising: an hermetically sealed, light-transmitting envelope; a quantity of filamentary combustible material located within said envelope; a combination-supporting gas in said envelope; and a primer secured to and extending from one end of said envelope and in communication therewith, said primer including a tube sealed in said end of said envelope and having an exposed segment outside said envelope, a wire anvil located within said tube and a body of fulminating material located on said wire anvil intermediate its ends and on that segment of said wire anvil located in said exposed segment of said tube but spaced from the inside wall tehreof.

2. The combination of claim 1 and means for supporting said wire anvil substantially coaxial with said tube.

3. The combination of claim 2 in which said support means includes at least one protuberance on the end of said Wire anvil located within said exposed segment of said tube.

4. The combination of claim 2 in which said support means includes at least one protuberance on said wire anvil intermediate its ends and above said body of fulminating material.

5. The combination of claim 2 in which said supporting means includes at least one protuberance on the end of said wire anvil located within said exposed segment of said tube and at least one protuberance on said wire anvil intermediate its ends and above said body of fulminating material.

References Cited UNITED STATES PATENTS 2,024,225 12/1935 Igari 43 l93 2,091,601 8/1937 Leijdens 43 l93 EDWARD J. MICHAEL, Primary Examiner 

